To: opendos AT delorie DOT com
X-Comment-To: Robert W Moss <domanspc AT juno DOT com>
References: <20001204 DOT 162239 DOT -446893 DOT 0 DOT domanspc AT juno DOT com>
Message-Id: <2.07b7.KRFT.G52LN7@belous.munic.msk.su>
From: "Arkady V.Belousov" <ark AT belous DOT munic DOT msk DOT su>
Date: Tue,  5 Dec 2000 04:04:19 +0300 (MSK)
Organization: Locus
X-Mailer: dMail [Demos Mail for DOS v2.07b7]
Subject: Re: BASIC & EMS (was: Optimizing CONFIG.SYS...)
Lines: 26
MIME-Version: 1.0
Content-Type: text/plain; charset=koi8-r
Content-Transfer-Encoding: 8bit
Reply-To: opendos AT delorie DOT com

X-Comment-To: Robert W Moss

Hi!

4-δΕΛ-2000 15:42 domanspc AT juno DOT com (Robert W Moss) wrote to opendos AT delorie DOT com:

RM> Virtual memory is not "memory".  It is the swap space on the
RM> hard drive which is used to opn up space in real memory by
RM> copying frequently used information out to the hard disk
RM> where the program can call it up when needed.

     Not necessarily. I.e. I mean this is only _one_ way to implement
virtual memory (VM). VM is a memory which exists as plain memory for
application which works in this memory, but it should be mapped into some
physical medium (RAM, disk, etc.). For example, some DOS extenders implement
swap files to increase available VM, other not.

RM> It is slow because it is limited to the access speed of the hard drive.

     _Only if_ part of VM, which must be accessed, currently swapped into
disk. If all used VM already mapped into phisycal memory then there is no
drawback, only advantages.

     Advantages: VM blocks can be moved in the physical memory to avoid
memory fragmentaion. VM allow to isolate separate application and prevent
one app memory contents corruption from other app.